In our new program emphasis will shift from exploratory studies concerning cell surface changes associated with transformation to a focused study of glycoprotein synthesis and function. We have recently shown that glucose addition occurs during the formation of lipid-linked mannosyl oligosaccharides and that the precursor form of at least one cell surface glycoprotein contains glucose. Careful analysis, however, shows that the mature glycoprotein lacks glucose. This result suggests new approaches to glycoprotein "maturation" or "processing" which we plan to follow up with in vitro enzymatic studies and parallel in vivo pulse labeling experiments. Much of this work will be carried out in cultured cells infected with Sindbis virus and VSV, systems in which precursor and "product" glycoproteins can be cleanly isolated. In another approach to the study of glycoprotein synthesis and maturation we will use Concanavalin A resistant mutants of mammalian cell lines. Recent preliminary studies in our laboratory have shown that at least one such CHO cell line mutant is defective in the synthesis of lipid-linked oligosaccharide intermediates of glycoprotein synthesis. The lectin resistant mutant approach should provide a powerful new tool for exploring the synthesis of glycoproteins. Equally exciting problems are developing in the area of glycoprotein function. The LETS or Z protein, a glycoprotein that we and others have found to disappear from the surface of transformed cells, has recently been shown to play a role in cell adhesion. We are anxious to explore this finding in detail and especially to see whether the substantial carbohydrate component of LETS is an active component in the adhesion process. These experiments will be carried out in collaboration with Dr. Richard Hynes. Finally, we are intrigued by recent developments concerning the mouse oncornavirus glycoprotein gp 70 and will initiate studies in this area in collaboration with Dr. Richard Lerner.